The present disclosure relates in general to semiconductor manufacturing technology, and more particularly, to reducing or solving precipitate defects associated with photolithography photomasks.
Photomasks, or reticles, are commonly used for photolithography in semiconductor manufacturing. Photomasks are typically made from very flat pieces of quartz or glass with a layer of chromium deposited on one side. The pattern being used to transfer an image to a wafer on BIM or PSM masks during a photolithography processing. While contamination of photomasks has always been a problem, high precision masks, such as are used in photolithography having wavelengths equal to or less than 248 nm, are particularly susceptible to defects.
One type of photomask contamination is referred to as haze contamination. Haze contamination is a precipitant formed from mask cleaning chemical residual or impurity of fab or tool environment cross exposure. For example, when a solution including ammonium (NH4) and sulfate (SO4) is used to clean a photomask, contamination becomes apparent when the photomask is exposed to a short wavelength UV light, such as 248 or 193 nm. Haze contamination maybe isolated by purging the photomasks with a general gas, such as nitrogen or clean dry air. Purging typically involves diffusing the gas into a reticle pod via a gas inlet and diffusing impurity materials, such as ammonium and sulfate, out of the reticle pod.
Photomasks also suffer from other defects, such as those caused from electrostatic discharge (ESD). ESD can damage the pattern on the photomasks, resulting in a defected image produced on the wafers.
Therefore, a need exists for a method and an apparatus that minimizes haze contamination. Also, a need exists for a method and an apparatus that reduce damages of photomasks due to ESD.